Electrically heated device



Feb. 6, c N ENT ELECTRI SALLY HEATED DEVICE Filed July 23, 1929llllliill!!! IIIIIIYIH INVENI'OR CARL M CLEMENT Patented Feb. 6, 1934PATENT OFFICE 1,945,628 ELECTRICALLY HEATED DEVICE 4 Claims.

This invention relates to electrically heated devices, and morepartiisularly to a novel means for thermostatically controlling suchdevices.

Electrically heated devies, including utensils for domestic use andcommercial equipment, have commonly been controlled by the mechanicalexpansion or distortion of thermo-electric couples or similar elements,depending in their action upon the heat generated in the device itself.The controlling device is thus subjected to extremely exactingconditions and cannot be depended upon for long life or for accuratecontrolling action after being used for any considerable length of time.It is with this general problem that my invention is concerned and itsobject is to improve the accuracy of thermostatic control, increase thelite and liability of action of the controlling means, and simplify theconstruction of the electrically heated device as a whole.

To this end I propose to employ a thermo-electric generator of thethermopile type for controlling the heating circuit of electricallyheated devices. I have discovered that a thermopile, working in a rangeof relatively slight temperature difference may be satisfactorilyemployed to operate a switch for'controlling the resistance of a heatingcircuit. Consequently, I am enabled to locate the thermopile outside thebody of the electrically heated device, where it is subjected torelatively slight temperature differences, which may be controlled byconnecting the thermopile to the electrically heated device byheatconductive members of the proper dimensions. In'one aspect,therefore, my invention consists in an electrically-heated device havinga heating circuit of adjustable resistance, a thermopile associated withthe device and arranged to beheated thereby, and an electricallyoperated switch in circuit with the thermopile and acting to control theadjustable resistance of the heating circuit.

An important field of use of my invention is in irons for domestic useand in this embodiment of the invention the thermopile maybe-convenient- 1y located in the handle of the iron, where it is removedfrom the direct and intense heat of the bodyof the iron. Preferably thesupports for the handle will be used as heat-conductive members. fortransmitting to the thermopile an amount of heat adequate to insure itseffective operation.

These and other features of the invention will be best understood andappreciated from the following description of a preferred embodimentCarl v. Clement, Beverly, Mass. Application July 23, 1929. Serial No.380,317

Fig. 1 is a view in horizontal section on the line 1-1 of Fig. 2;

Fig. 2 is a view in vertical section;

Fig. 3 is a view in cross section of the handle on the line 33 of Fig.2; and

Fig. 4 is a diagrammatic view of the thermopile and the electriccircuits of the device.

I have illustrated my invention as embodied in an iron having a solidbase portion G, above which is formed an enclosed chamber by a sheetmetal shell T held firmly to the baseby four vertical bolts J. A heatingcoil of resistance wire Q extends about themargin of the base G and isconnected at one end to a lead-in terminal P. The upper portion of theshell 'I is thickened to form a supporting plate, to the under side ofwhich is secured an auxiliary resistance coil R connected at its rearend to the resistance coil Q and at its forward end to the secondlead-in terminal P. Beneath the auxiliary resistance coil R is secured aleaf spring U, constituting one element of a switch, as willpresently-be explained, andacting normally to short circuit theauxiliary resistance coil R by contact with it throughout its'length.The spring or switch member U is secured to the shell by a screw Y,which also assists in holding in place a strip of insulating materialwhich is interposed between the auxiliary coil R and the thickened partof the shell-T.

Secured to the base G of the iron is an electromagnet N, comprising twohorizontally disposed coils and an armature M pivotally secured to thecore of one coil and having a curved slot for the reception of the coreof the other coil, whfi feby it may be swung up or down about itsrighthand end, as seen in Fig. 2, for purposes of adjustment. The upperportion of the armature lies beneath the free end of the switch member Uand in position to deflect this member downwardly and away from theauxiliary resistance coil B. when the electro-magnet N is energized. Theposition of the-armature M is adjustably controlled by a verticaladjusting screw W which extends freely through the shell T at its upperend, where it is provided with a head by which it may be convenientlyturned. At its lower end it threaded into the armature and when turnedin a clock wise direction will lift the free end thereof, bringing itcloser to the under side of the switch member U so that the latter willbe more delicately responsive to the energizing of the electro-magnet N.y

The handle of the iron is connected to the body portion by a metallicstrip V bent upwardly at both ends and thus forming two spaced heatw, I,illoM ,1.

the rods ternately at their handle, as shown in l. bly is containedwithinan insulating shell in serted in the handle of the iron. Thethermopile is electrically insulated at each end by disks D of suitablematerial which are engaged by a pair of metallic disks E connected to orformed as a part of the heat-conductive members V.

The thermopile is disposed in circuit with the electro-magnet N in thebody of the iron, being connected thereto by insulated wires K and Lwhich pass down the rear heat-conductive member through the shell T andto the-electro-magnet N.

In Fig. 4 I have diagrammatically illustrated the two circuits using thesame reference characters as are applied to the device itself.

Referring particularly to Fig. 4, it will be seen that one lead-interminal P is connected to the principal resistance coil Q and that thecircuit extends from the outer end of the coil Q to one end of theauxiliary resistance coil R, and from the other end of the resistancecoil it back to the second lead tin terminal. The flexible switch memberU is shown as short-circuiting the auxiliary heating coil R. Thethermopile 4A B is shown as in circuit with the electromiagnet N, and Mrepresents the armature of the magnet which is lo cated in proximity totheswitch member U.

In operation, the iron is connected to a power circuit at the lead-interminals 1? and the body of the iron is gradually heated by the heatgenerated in the principal resistance coil Q. As the hotly of the ironincreases in temperature, heat is conducted upwardly through the spacedheat-conductive branches or the member V and the disks E at the outerends or the thermopile are warmed. This continues until the temperaturedifference between the ends 01' the thermopile and the center thereof,where the thermo-electric rods are joined, is suflicient to generate acurrent in the thermopile circuit, thus energizing the electromagnet, Nand moving the switch member U downwardly into contact with the armatureM and out 0! contact with the auxiliary resistance coil R. When thisoccurs, the additional resistance of the auxiliary coil R is cut intothe main heating circuit. The current is correspondingly cut down andthe device as aJWhofle is reduced in temperature. The switch member U,however, is held down as long as current is being generated in thethermopile and heating of the irony con and the e its ini As a tiegoverning e resistcircuit as above tplained,

temperature or the body of the iron may be .cintained uniform within afew degrees of temperatnre.

"While I have disclosed my invention as embodied in a sad iron, it willbe understood that it may be embodied with equal advantage in anelectrically heated soldering iron, curling iron, or any otherelectrically heated utensil for domestic purposes, or in an electricallyheated wax pot, shuttle case, or electrically heated commercialequipment of any other type.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. An electrically heated device having a heating circuit of adjustableresistance, a thermcpile mounted outside said device, heat conductivemembers extending between said device and thermopile, and anelectrically controlled switch associated with the thermopile and actingto govern said adjustable resistance.

2. an electrically heated device comprising an operative member having aheating circuit of adjustable resistance for heating the same, anelectro-magnet, a switch associated therewith for controlling theheating circuit, a pair of spaced heat conductive members projectingfrom said operative member, and a thermopile mounted between the outerends of said heat-conductive members and disposed in circuit with saidelecho-magnet.

3. An electrically heated device comprising an operative member having aheating circuit of adjustable resistance for heating the same, anelectro magnet having an adjustable armature, a resistance-controllingswitch arranged to be 011-- erated by said electro-magnet and governedin its action by the setting of the armature, a heatvconductive memberconnected to said operative member, and a thermopile carried thereby anddisposed in circuit with said electrc-magnet.

4. An electrically heated, thermostaticallycontrolled iron having aheating circuit of adjustable resistance in its body portion and also anelectro-magnetically operated switch for governing said heating circuit,and a thermopile located in the handle of the iron, having thermalconnection to the hotly thereof and being disposed in circuit with saide1ectro-magnetically operated switch.

CARL Claim/TENT.

